Because of the variability in the definition of COPD in epidemiological studies, an accurate prevalence of this disease is difficult to determine. The prevalence is approximately 14% in smokers, 7% in former smokers and 3% in individuals who never smoked ( 3 ). Surveys on the prevalence of asthma suggest a prevalence of approximately 9% in the British population. In Brazil, an epidemiological study of the population in São Paulo revealed a COPD prevalence of 15.8% ( 4 ), whereas the prevalence of asthma was estimated to be approximately 10% of the general population ( 1 ). Several studies have suggested a similar prevalence of asthma among children and adult populations; however, extensive variability has been found depending on multiple factors that include geographic differences and socioeconomic status ( 5 ).